Telephone automatic trunk-selecting system.



M. SETTER. TELEPHONE AUTOMATIC TRUNK SELECTING- SYSTEM.

APPLICATION FILED MAY6} 1910.

Patented July 21, 1914.

4 SHEETS-SHEET 1f lM ENTDR:

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[Mm/E3353 M. SETTER. TELEPHONE AUTOMATIC TRUNK SELECTING SYSTEM. APPLICATION FILED MAY 6, 1910.

Patented July 21, 1914.

4 SHEETS-SHEET 2.

M. SETTER. TELEPHONE AUTOMATIC TRUNK SELECTING SYSTEM. APPLICATION FILED MAYB, 1910.

1,104,45 1 Patented July 21, 1914 4 SHEETS-SHEET- 3.

MT/V5555? Amen/70R- M. SETTER. TELEPHONE AUTOMATIC TRUNK SELECTING SYSTEM. APPLICATION FILED MAYG, 1910;

4 SHEETS-SHEET 4i Patented July 21, 19m

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MIGHAEL. SETTER, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHECAGO, ILLINOIS, A CORPORATION OF ILLINOIS TELEPHONE AUTOMATIC TRUNK-SELECTING: SYSTEM.

To all whom it may concern:

Be it known that 1, MICHAEL SETTER, a citizen 'of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Telephone Automatic Trunk- Selecting Systems, of which the following is a specification. a

My invention relates to telephone exchange systems in which means are provided for automatically selecting idle trunks-in response to a calling subscriber, or a calling operator, depending upon whether the system is entirely automatic or semi-automatic in character.

As hereinafter described, my invention contemplates an automatic switch of such character that it will automatically select idle trunks by a continuous movement of the wipers thereof from one trunk terminal to another, as distinguished from the step-bystep'movement heretofore employed for this purpose, and in which the said continuous motion is supplied by suitable motive power, preferably an electric motor, as will hereinafter more fully appear.

To the foregoing and other useful ends my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings Figures 1 and 2 show a complete circuit connection be tween a calling substation A and a called substation A in a system embodying the principles of my invention. Figs. 3 and 4 are a top and front view, respectively, of my improved master switch. Fig. 5 is a view representing the manner in which the master switch is connected to the plunger shaft which it controls.

In Fig. 1 there is shown an automatic substation the line conductors of which are connected to an individual switch C at the central oflice. A group of these individual switches U is controlled by one of my im proved matically at D.

of which terminates in a selector switch E. A group of selector switches E has common master switches represent ed diagram- Each group of switches C has access to a plurality of trunk lines, each Specification of Letters Patent. Patented J l 121 r914 Application filed May 6,1;910. Serial no. 559,826.

access to a number of trunk lines, each of .which terminates in a connector switch F number of other similar switches, has access ,to a group of substations of which the sub- 1 station A is a member. At the central office there isal-lotted to the substation A an individual switch C similar to the switch C (Fig. 1). At L there is shown a ringing current generator, and at M a busy Signaling machine is shown. At B there is shown a battery, having one pole grounded, which su plies current for operating the central o co apparatus and for furnishing talking current. V p

, The automatic substations A and A may be of any suitable or approved type. As illustrated at A the substation with which I have elected to illustrate my invention con'iprises a receiver 2, switch h0Ol 3', trans- .initter 4, ringer 5, condenser 6, impulse springs 7 and 8 and impulse wheel 9; The switch hook 3 controls the substation circuits through the medium of springs 10, 11" and 12. The impulse wheel 9 carries upon its periphery a number- 0f impulse teeth 14. and is secured to the shaft. 13, to which latte-r there is also secured a (not shown) provided with finger holes. In order to make a call the receiver is removed from. the switch hook, a finger is inserted in the opendigit of the desired number, the dial is rotater. until the finger strikes a stopand is thenallowed to be returned to normal position by a spring (not shown). This operation of thedial is repeated in succession for each digit. Asthe dial is rotated forward, a number of impulse teeth lat, corresponding to the digit to be called, are advanced past the end of the impulse spring 7 The imthe forward rotation of the dial the springs 7 and 8 are not separated, but each tooth that passes the end of the spring? during the backward rotation of the impulse wheel momentarily forces thespring 7 out of engagen-ient with the spring 8.

I (Fig. 2). The connector F, together with a pulse teeth 14 are so arranged that during ing of the dial correspondin to the first V The sub scribers individual switch C(Fig. l

1) is of the general type disclosed in British Patent No. 26,301 of 1906, but is of a slightly modified construction. The line switch 0 is provided with a plunger which is not shown in Fig. 1, but isrepresented at 81 in Fig. 5. The plunger 81 is attached to a plunger arm 82' (Fig. 1) which is under the control of themagnet 83. The magnet 83 also controls two relay armatures 84 and 85. This magnet comprises four windings 86, 8'7, 88 and 89 designated, respectively, as a pull-down winding, a bridge-cut-oif winding, a line winding and an auxiliary winding. The collar 90, which is a part of the core of the magnet 83, is secured to the bracket to which the armatures 82, 84 and 85 are pivoted, and thus the magnetic circuit of the windings 86 and 87 is separate and distinct from that of the windings 88 and 89. The energization of the .windings 86 and 87 affects only the rangement it is evident that when the wheel armatures 82 and 84, while the armature 85 is attracted only by the energization of-the windings 88 and 89. The energization of" the winding 86 upon the upper end of the magnet serves to attract both the plunger arm 82 and the armature 84. The magnetic effect of the winding 87 is much weaker than that of'the winding 86, and since the plunger arm 82 is normally separated from the core of the magnet 83 by a greater distance than the armature 84, and is held in this position by. a stronger spring, the energization of the winding 87 alone operates only the armature 84. If, however, the winding 87 is energized while the lunger arm 82 is in its operated position, it will be held in this position by the winding 87 after the circuit of the winding 86 is oken. When the plunger arm 82 is attracted by the magnet 83, the plunger on the end of this arm is driven into a group of contact springs 91,

92, 93, 94,95, 96, 97 and 98 to force them into contact in pairs, as indicated in the drawings. Although only one group of springs (91-98) is shown, each switch C is provided with a number of such groups, each I group forming the terminal of a trunk line which terminates in a selector switch E. Each one of these trunk lines is connected to the corresponding contact springs of a number of switches C. These groups of, contact springs of each switch are arranged upon a circular are just in front of the point of the plunger 81. The other end of this plunger is provided with a fan-like projection, in the center of which there is a notch which is adapted to register with a flange 99 upon a so-called plunger shaft 100 (Fig. 5) when the plunger is in its normal or retracted position. The plunger shaft is controlled by a so-called master switch D and is always held thereby in such a position that the plungers which are in looking engagement with the said shaft are in front of the ter-' minal of a trunk line which is not already in use by some other switch.

The master switch D is shown diagrammatically in Fig. 1, but more fully in Figs. 3, 4 and 5. Referring to Figs. 3, 4 and 5, the construction of the master switch is as follows: In Figs. 3 and 4, 101 represents an ordinary small electric motor. The shaft of this motor is detachably connected, to a pinion 102 which meshes with a gear wheel 103. This gear wheel 103, together with a toothed wheel 104, is rotatably mounted upon a shaft 106 which projects from the frame 107. On the face of the wheel 103 there is a cup 108 in which is placed a flat coiled spring 109. The outer end of the spring 109 is secured to the inside of the cup 108, while the other end of the spring is secured to the hub 110 of the wheel 104 which extends inside the cup 108. With this ar- 103 is rotated in a clock-wise direction by the motor 101, the,wheel 104 will tend to 5 turn in the same direction, but if the wheel F 104 is held stationary by any means, the rotation of the wheel 103 stores up tension in the spring 109 until the motor is stopped. The teeth of the wheel 104 register with a worm gear 111, to one end of which is secured a pair of governor springs 112, while the other end is provided with a locking member 114. The locking member 114 nor- ;mally engages the lug 115 upon the end of ;the armature of relay 116, whereby the worm gear 111, and consequently the Wheel 1104, is effectively locked against rotation. ,When the relay 116 is energized the lug 115 disengages the locking member 114, which iallows the wheel 104 to be rotated until the ,relay .116 again becomes deenergized. The speed of rotation of the wheel 104 is gov- }erned by the governor springs 112. When ,the-speed becomes too great the weights on the ends of the springs 112 move outward Qand rub on the sides of stationary cup 117, thus by their friction retarding the move- }ment of the gear 111 and wheel 104. From gthe back of the wheel 104 a pin 118 projects jinto the path of a pin 119 which projects Efrom the front of the wheel 103. lVhen the :wheel l04'is looked, as has been explained, ;the motor 101 rotates the wheel 103 until ,the pin 119 strikes the pin 118, when the ;motor and wheel 103 are stopped also. Referring now particularly to Fig. 5, the wheel 104 is connected with the plunger fshaft 100 through the medium of the link E120 in such a manner that the rotary motion lof the wheel 104 causes the shaft 100 to oscillate back and forth about the shaft 121 ,as an axis. This oscillation of the plunger Eshaft 100 causes the point of the plunger 81 ;to be moved back and forth in front of its jtrunk terminal springs. The connection be.

pherical cavity in each plate is formed in a projection that extendspartly through an opening, in the wheel 101. These projections meet when the plates 283 and 282 are clamped in place, so that the ball 281 is com- 4 pletelyinclosed except at the top, where an opening is cut through the face of the plate 283 to permit the end of the link 120 to project into the opening 281 in the ball 281. The plates 282 and 283 are clamped to the wheel 101 by screws 285 and 286 which pass through openings in the plate 283 and wheel 101 into threaded holes in plate 282. The openings 287 and 288 in the wheel 101 are made in the form of slots in order that the plates 282 and 283 may be moved toward or away from the center of the wheel, so as to adjust the'length' of stroke of the plunger shaft 100. Theimaster switch is also provided with a bank or group of contacts, which group comprises an individual segment 122 for each trunk to which the switch (7 has access and one common segment 123. The wiper 121 is adapted to always keep the individual contact which corresponds to the'trunk line before which the idle plungers are resting in electrical connection With the common segment.

Briefly, the operation of the master switch D is as'follows: The motor 101 is permancn11y connected to battery-and is thus alwaysenergiz ed. keeping the spring 100 under tension. YVhen a subscribers individual switch operates, its plunger disengages the plunger shaft and enters the group of contact springs before which it is being held by the plunger shaft 100. hen the plunger thus operates. the relay 116 is energized,

" its circuit including the wiper 121 and the individual segment upon which it is resting. As soon as the relay 110 is energized the locking member 111 is released, allowing the wheel 101 to be rotated forward by the spring 100. As soon as the wheel 101 has moved far enough to rotate the wiper 121 off the contact which corresponds to the trunk line which was seized by the switch which just operated, the relay 110 deenergizes and instantly locks the wheel 101 1 again. T his forward movement of the wheel 104- and plunger shaft 100 moves the idle plungers which are engaged with the shaft away from the terminal of the busy trunk to an idle one. Of course, as soon as the wheel 101 is moved, as .just explained, the pin 118 leaves the pin 119, whereupon the motor 101 moves the wheel 103 forward to restore the tension to the spring 109. .As soon as the pin 119 catches up with the pin 118'the motor again stops. The reason that a spring is used to move the plunger shaft, rather than allowing the motor to do so directly, is that the spring responds much more quickly than the motor when the mechanism is unlocked.

The selector switch E is of the well-known type disclosed in United States Letters Patent #815,321, granted March 13, 1000, to Keith, Erickson and Erickson. As herein represented, however, the circuits of the selector E are somewhatmodified to enable it to be operated in a system in which the switches-are controlled over the two sides of the line in series. Among other details, the selector E comprises a set of wipers 131, 132 and 133 which are carried upon a shaft having a vertical movement controlled by the vertical magnet 131, and a rotary motion under control of the rotary magnet 135. The side switch. comprising the wipers 130, 137, 138 and 13!), controlled by the socalled private magnet 110 in a well-known manner. The usual vertical and rotary line relays are here combined in one doublewound relay 111. The relays 112, 113 and 111 are relays that deenergize slowly after their, circuits have been broken. This slow action is usually accomplished by placing a heavy ring of copper around one end of the magnet core. Means for releasing the switch are provided in the release magnet 115,

which is always disconnected from the battery except when the shaft is raised one or more steps, thereby allowing the spring 110 to engage spring 117. The mechanism of the selector E is released immediately upon the energization of the release magnet, rather than by its 'deenergization, as shown in the said select-or patent. The selector is also provided with a group or bank of con tacts which are adapted to be engaged by the wipers 131, 132 and 133 and which form terminals of trunk lines leading to connector F (Fig. 2). r

The connector F is of the general type disclosed in United States Letters Patent #815,176, granted March 13, 1000. to Keith, Erickson and Erickson, and its mechanical features are very similar to those of the selector E. The connector 1 is provided with a so-called back-bridge relay 118 through the windings of Avhich the. called substation is provided with talking battery current. A ringer relay' 119 is provided for the purpose of controlling the application of signaling current to the called line.

Having given a description of the appato be performed in making a call is to remove the receiver from the switch hook. WVhen the receiver is removed the hook 3 rises, allowing spring 11 to disengage spring 12 and engage spring 10. The disengagement of the springs 11 and 12 opens the circuit through the ringer 5, and the engagement of the springs 10 and 11 closes a bridge across the line conductors ,150. and 151, which bridge includes the impulse springs 7 and 8 and the windin of the receiver 2. The closure of this bridge across the line completes an energizing circuit through the line winding 88 ofit-he switch C. This circuit extends from ground G through springs 152 and 153, thence over line conductor 150 through the springs 11 and 10, impulse springs 8 and' 7, receiver 2, transmitter 4, thence back over line 15.1 and through springs 155 and 154, winding 88 to the battery lead 168 thence through the battery B to ground The winding '88, upon bein energized, attracts the armature 85, whic forces the spring 157 into engagement with spring 152, thereby closing a circuit through the pull-down winding 86. This circuit extends from ground G through the springs 152 and 157, and through windin 86 and '89 and springs 158 and 159 to tie battery. lead 168, thence through the battery-B to ground G. The winding 86, upon energizing, attracts the plunger arm 82 and cut-ofi armature 84, as has been previously explained. The armature 84 operates to press springs 153 and 155 away from s rings 152 and 154, re'-' spectively, and to orce s ring 155 into contact with spring 160. 'l he enga ement of springs 155 and 160 has no particlilar utility at this time. The disengagement of springs 153 and 155 from the springs 152 and 1-54 disconnects the winding 88 and ground G from the line conductors. The armature 85 is closed t does not fall back. immediately upon the breaking of the circuit of the win ing 88, but remains held up for an instant by the current flowin through the winding 89 in series. with t e winding 86. When the plunger .arm 82 is operated by the magnet 83 it not only forces the springs 91 and 92, etc. into contact, as previously explained, but forces the spring 161 into contact with the contact point 162. The engagement of springs 161 and 162 short-circuits the auxiliary winding 89, which allows the armature 85 to return to normal position to break the circuit through the pull-down winding 86. Before this circuit is broken, however, the circuit of winding 87 is closed asfollows: At the instant the springs 91 and '97 are forcedintocontact wlth the springs 92 and 98 by the lunger of the switch 0, a circuit lirou ghthe line .relay 141 ofthe selector .13. his circuit extends from groundlfi through the;winding.1'63 .of relay transmitter 4,

' of the idle switches 141, through side switch wiper 137, contact springs 98 and 97, line 150, thence through the substation A and back over line 151, through springs 91 and 92, side switch wiper 136 and Winding 164 of relay 141 to the battery-lead 168. The relay 141, upon energizing, operates to shift the spring 165 outof engagement with spring 166 and into contact with spring 167, thereby closing a circuit through the relay 142. This circuit extends from ground Gr through the springs 165'and 167 and through the relay 142 to the battery lead 168. The relay 142, upon energizing, shifts the spring 169 out of engagem'ent with thespring 170 and into c0ntact with the spring 171, and closes contact between the springs 172 and 173. The engagement of the springs 172 and 173 closes a circuit extending from ground G through springs 172 and 173, springs 94 and 93, and through the winding 87of the switch C to battery lead 168. This current through the winding 87 maintains the arm 82 and armature 84 in an operated position, ashas been previously stated. The engagement of springs 172 and 173 at the selector E extends a guarding potential from the ground G to the conductor 174, and thence to the private bank contact corresponding to the line of substation A in the bank of all the connector switches which have access tothat line. This guarding potential prevents the line from being seized for connection while it is in use.

At the instant that the springs 95 and 96 are forced into contact by the plunger of the switch C, the relay 116 l) is ener ized over a circuitextending from ground through the springs 95 and 96, contact point 122, wiper 124, segment 123 and relay 116 to battery lead 168. The relay 116,"dpon energizing, unlocks the wheel 104, allowing it to rotate to move the plungers away from the terminal of the trunk line which has just been seized. As soon as the wiper 124 leaves the contact 122, the relay 116 deenergizes and again locks the wheel 104, with the idle plungers resting in frontof the terminal of the next trunk. If this next trunk is busy, however, the .wiper 124 will find the corresponding contact grounded, the relay 116 will remain energized and the plungers will be advanced past the busy trunk or trunks-to an idle one. It will be noted that as long as the relay 116 is energized, and, consequently, as lon as the master switch is operating, the springs 158 and 159 are-separated, thus dis? connecting the winding 88 of all the switches C which are controlled by the master switch of the master switch 1) from the battery lead 168. This prevents the possibility'of any subscribers switch being 0 rated while its plunger is being move from one trunk to another.

, The. foregoing are ,the '.l.:0pera.tions.,which;

meager -i'ollow immediately upon the removal of the receiver trom the hook, and before the calling device is operated. Now, when the calling device is operated for the first digit 2 5 the impuise springs 7 and 8 are separated twice momentarily. Each time these springs are separated, the relay 141 at the selector E deenergized to permit the spring 165 to disengage spring 167 and engage spring 166. 1 Since the disengagement of springs 105 and 167 is only momentary, the slow-acting relay 14 does not have time to deenergize and, consequently, the engagement of springs 165 and 166 closesan energizing circuit through the vertical magnet 131. This circuit extends from. ground G through springs 165 and 166, springs 169 and 171, private magnet relay 143, vertical magnet 13 1, contact point 175 and side switch wiper 138 to battery lead 168. Since the digit called is 2 the vertical magnet receives two impulses, operating to raise the switch shaft two steps to carry the wipers 131, 132 and 133 two steps to a point opposite the second row of bank contacts. '25- The private magnet relay 143, which is included in the circuit with the vertical magnet 13-1, is energized by the first impulse, but being a slow-acting relay does not have time to deiin'ergize between impulses. When the 3 ;;rclay 1&3 energizes it operates to close a circuit through the private magnet 140. This circuit extends from ground G through springs 178 and 177 and magnet 140 tothe battery lead 188. Shortly after the last imlgmpulse is delivered to the vertical magnet the relay 1-13 de inergi'zes to break the circuit of the private magnet 140. The magnet 1 10 thereupon dehncrgizes and allows the side switch to pass from first to second position. {40 The side switch wiper 138,'by passing from contact 175 to contact 178, disconnects the battery from the vertical magnet 134 and closes a circuit through the rotary magnet 135. This cirruit extends from ground Gr 5 through int. rupter springs 179, rotary magnet 135, Many 14:4, contact point 178 and side switch wiper .33 to the battery lead 168. The rotary magnet, upon energizing, attracts its armature, which rotates the wipers 131, 132 and 133 one step,presses down the armaturc'of the private magnet 1 10, and brcaks'the circuit of itsfown magnet by separating the interrupter springs 179. \Vhen the circuit of the rotary magnet is thus broken its armature falls back, and, if the vtrunk line upon the terminals of which the S'vluuliOl wipers are rotated by the first step is: not already in use, the armature of the private magnet falls back also, permitting 0 the side switch to pass to third position to cxtend the line connection to the trunk line. If, however, the first trunk line is busy, the contact which is engaged by the private wiper. 133 is provided with a guarding .65 ground potential, as will be explained later.

hen the wiper 133 thus engages a grounded contact a circuit is completed extending from this contact over coiuluctor 180, through side switch wiper 13$), contact point 181, (the side switch being in second posi- :tion), thence through the private magnet 1410 to the battery lead 168. The private magnet thereupon locks the side switch in second position, whereby the circuit of the rotary magnet 135 is again closed as soon as its armature returns far enough to permit the springs 179 to again engage. The rotary magnet, upon energizing a second time, r0 tates the selector wipers .a second step onto the terminals of the second trunk line. The wipers will thus be rotated step by step until the wiper 133 strikes the non-grounded contact of an idle trunk, whereupon the private magnet 140 becomes deenergized and allows the side switch to pass to the third position to break the operating circuit of the rotary magnet at the wiper 138.

The movement of the side switch wipers 136 and 137 from second to third position disconnects the selector line relay 1441 from the line and extends the line connection through the shaft wipers 131 and 132 to conductors 182 and 183 which lead to the connector F (Fig. 2). The extension of the connection to the connector causes its line relay 185 to become energized over a circuit extending from ground G through winding 186 of relay 185, trunk conductor 183, and from conductor 183 the circuit ex- 2 tends over the heavy conductors of Fig. 1 to and through substation A and back to the connector F over the other side of the line, and through winding 187 of relay 185 ;to battery lead 168. The relay 185, upon energizing, operates to close a circuit through the relay 188', which corresponds to the relay 142 of the selector E. This circuit extends from ground Gr through springs 189 and 190 and through relay 188 to battery lead 168. The closure of contact between springs 191 and 192 by the energization of relay 188 extends a circuit from ground G through side switch .wiper 193, springs 192 and 191 and conductor 1841 to the private bank contact upon which the selector wiper 133 is resting, and to the corresponding contact in-the private bank of all the selectors which have access to the trunk conductors 182 and 183. The ground potential upon the private bank contacts prevents any other selector E from stopping on the contacts of the busy trunk. From the private bank contacts a circuit also extends through the wiper 133 of the selector E over ,the conductor180, through the side switch wiper 139 (in third position) springs 194i and 195 of the relay 144: and

through the r.elay.14r2 to the battery lead I 168. This circuit through the relay 161-2 is closed before the relay has time to denergize after its former circuit is broken by the dciincrgization of the relay 141 when the side switch leaves second position. A short period of time elapses between the time when I the side switch of the selector passes to third bank contacts during this last two digits energizes it closes position and the time when the relay 188 of the connector energizes. In order to supply a guarding potential to the selector private short period of time the relay 144 is provided. It will be remembered that this relay 144 is included in the energizing circuit of the rotary magnet 136, and, since it is a slow-acting relay, it remains energized for an instant after the rotary magnet is energized the last time. Thus, at the instant the side switch wiper 139 reaches the third position a guarding potential is extended from groundG through the springs 196 and 194, side switch wiper 139, conductor 180 and private wiper 133 to the private bank contacts. Of course, the relay 144 must be quicker than the relay 142 in order to close the circuit of the latter relay at the springs 194 and 195 before it has time to denergize.

The central oflice apparatus is now in position for the reception of the impulses for the of the desired number, which digits affect the connector F to cause it to extend the connections to the desired line. The operation of the substation calling device for the second digit 2 opens the line circuit twice in the same manner as explained for the first digit. In this case. however, the opening of the line allows the line relay185 of the connector F to be denergized momentarily. Each time the relay 185 dea circuit extending from ground G through springs 189 and 197, 198 and 199, vertical magnet 200, side switch wiper 201 and private magnet relay 202 to battery lead 168. Since the digit called is 2 the vertical magnet receives two impulses,

thus operating to raise the connector wipers- 203, 204 and 205 two steps to a position opposite the second row of contacts, in which row are situated the terminals of line #220. The private magnet relay 202 operates in a manner similar'to of the selector E to closethe circuit of the private magnet 206 while the vertical magnet is operating. This circuit extends from ground G through springs 207 and 208 and magnet 206 to battery. Shortly after the last impulse of the second digit is delivered, the relay 202 denergizes and opens the circuit of the private magnet 206. which in turn deenergizes to permit'the side switch to pass to second position. The movement of side switch wiper 201 transfers the battery connection from the vertical magnet 200. to the rotary magnet 209. Each time the relay 185 de'e nergizes inresponse to the impulses for the last digit 0 a circuit is closed through the rotary magnet 209. This circuit-extends rom ground G through springs 189 and that of the relay 143.

197, springs 198 and 199, springs 210 and 211, rotary magnet 209, contact point 212, side switch wiper 201 and relay 202 to the. battery lead 168. Since the digit called is 0 the rotary magnet 209 receives ten impulses over this circuit, operating to rotate the wipers ten steps onto the contacts of the desired line. The private magnet relay 202 operates in the same manner as for the previous digitto close the circuit of the. private magnet 206 While the impulses are being delivered.

After the last impulse for the last digit is delivered, the private magnet relay 202 deenergizes. If the desired line is idle when ,thls relay deenergizes the private magnet 206 deenergizes also, permitting the side switch to pass from second to third position. I

The engagement of the side switch wipers 213 and 214 with their respective third-position contact points extends the connection from the calling line to the called line through the shaft wipers 203 and 204. The movement of side switch wiper 215 from'sec- 0nd to third position establishes a guarding potential upon the connector private bank contacts of the called line, and also provides an energizing circuit for 219 of the switch C. This circuit extends from ground (it through side switch wiper 215, springs 220 and 221, private. wiper 205, bank contact 222 and corresponding contact in the other connectors which have access to line #220, and through winding 219 to battery lead 168. The winding 219, upon energizing, attracts the armature 223, which operates to disconnect the switch C from the called line and to extend connection from the contact upon which wiper 203 to the line conductor 224. The movement of the side switch wiper 201 from second" to third position disconnects the rotary magnet 209 from the battery and completes an energizing circuit for the ringer relay 149. This circuit extends from ground G through the interrupter 216, springs 217 and 218, relay 149-, side switch wiper 201 and relay 202 to battery lead 168. The relay 149, upon'energizing, shifts springs 226 and 229 out of engagement with springs 227 and 230 and into contact with springs 225 and 228, respectively, whereby the calling line is disconnected from the called line and the terminals of the ringing current generator L is bridged across the called line. Ringing current thcn flows 'from one terminal of the generator L through springs 225 and 226, wipers 213 and 203. springs 231 and 232, line 224, ringer- 233, condenser 234, hook switch springs 235 and 236. line 237. wiper 204, side switch wiper 214-. relay springs 229 and 228, back toihe opposite terminal oi the generator M. Since the energizing circuit'ot the ringer relay 149 includes the interrupter 216, this relay is energized only intermitthe cut-off winding is resting tently, so as not to ring the bell 233 continuously. As soon as the receiver at the substation A is removed from the hook in answer to the signal, or as soon thereafter as the ringer relay is dcenergized if it happens to be energized at the time, the substation is provided with talking current. The circuit over which this current flows extends from ground G through side switch wiper 215, winding 238 of relay 148, ringer relay springs 230 and 229, side switch wiper 214, wiper 204, line 237, receiver, calling device and transmitter at substation A, hook switch springs 239 and 236, line 224, springs 232 and 231, wiper 203, side switch wiper 213, springs 226 and 227,-and winding 240 of relay 148 to battery lead 168. The relay 148 is energized upon the completion of this circuit and, by separating springs 217 and 218, breaks the circuit of relay 149 to prevent the further application of ringing current to the called line.

After the conversation is completed the release of the central oiiice apparatus is initiated by the restoration of the receiver to the switch hook at the calling substation. When thespring 11 disengages the spring 10 upon the hanging up of the receiver at the substation A, the circuit of the connector line relay 185 is permanently broken and the said relay deenergizes. The separation of springs 189 and 190 of the relay 185 destroys the energizing circuits of the release relays 188 and 142 of the connector'F and selector E, respectively. Although it has not been stated, it is evident that by the passage of the connector side switch wiper 193 from second to third position, the holding ground of the release relay 142 of the selector E is transferred from the ground G to the ground G which is connected with the third-position contact point of the side switch wiper 193 through the springs 189 and 190 as long as the relay 185 is energized. The relays 188 and 142 both deie'nergize 'shortly after their circuits are broken and operate to close the circuits of the release magnets of their respective switches. The circuit of the release magnet 241 of the connector F extends from ground G through the springs 189 and 197, 198 and 242, magnet 241 and off normal springs 343 and 344 to the battery lead 168. The circuit of the release magnet 145 of the selector E extends from ground G? through the springs 165 and 166 of the relay 141, springs 169 and 170, magnet 145 and oii normal springs 146 and 147 to the battery lead 168. The energ-ization of the release magnet 241 allows the mechanism of the connector F to be restored to normal position, which breaks the connection with the called line and destroys the energizing circuit of the cut-off winding 219 of the individual switch C. When the shaft I of the switch returns to its lowest position the spring 343 is carried outof contact with the spring 344, which breaks the energizing circuit of the magnet 241, thus leaving all relays and magnets of the connector deenergized. The mechanism of the selector E is released by theenergization of the magnet 145, after which the circuit of this magnet is broken by the separation of springs 146 and 147, when the switch shaft reaches its lowest position.

The deencrgization of the relay 142 at the selector K not only closes the release circuit of that switch, as has been explained, but it also destroys the holding circuit of the winding 87 of the switch C by the separation of springs 172 and 173. The deenergizing of the winding 87 oft-he switch 0 allows the plunger arm 82 and cut-oil armature-84 to be restored to their normal positions, and thus all the apparatus employed in establishingthe connection is left in position for immediate use again.

In the foregoing it ha been explained how connection is completed with an idle or non-busy line. It will now be explained how the connector F prevented from completing the connection and the calling subscriber is given the busy signal in case the line wanted is already in use when called. When a busy line is called, the operations are just the same as those explained up.to the point where the private magnet relay 202 of the connector denergized after I guarding potential is supplied by av selector switch, while for called lines the guarding potential is supplied by the connector switch by which the connection was completed.

Thus it will be seen that had the line #220 been busy when called from substation A, there would have been present a guarding ground potential upon the private bank contact 222. At the instant the wiper 205 is rotated onto a contact that is thus grounded, this ground potential is extended through the springs 221 and 220 of the relay 243, winding 238' of the relay 148, ringer relay springs 230 and 229, side switch, wiper 214 and contact point 244 to the spring 245 of the relay 202.' When the relay 202 deenergizes, the spring 208 engages the spring 245 before it disengages the spring 207, and thus when the called line is busy the ground G is replaced by the ground at the private bank contact, which causes the private mag net 206 to remain energized, locking the side switch in second position. Since the winding 238 of the relay 148 is included in the locking circuit of the private magnet 206, this relay is energized also. I The simultaneous energization of 'the relay 148 and private magnet 206, together with the deenergization of the relay 202, completes a circuit extending from ground Gr through springs 207 and 246, 247 and 248, relay 2 13 and springs 249 and 250 to battery lead 168. The relay 24:8, upon energizing, disconnects the rotary magnet 209 from the impulse spring 197, shifts the holding ground of the private magnet 206 and relay 148 to ground Gr without breaking its circuit and connects the busy signaling machine M with the calling line. The circuit over which the busy signaling curren" flows extends from the battery lead 168 through the secondary winding of the machine M, springs 251 and 252, side switch wiper 213 (which is locked in second position), ringer relay springs 226 and 227, condenser 258, thence over the heavy conductors shown in Figs. 2 and 1 to and through substation A and back over the other side of the line to and through the winding 186 of the connector line relay 185 to ground G, and thence through the battery B to the starting point. Of course, during the time the calling substation is receiving the busy signal, said substation has no connection with the called line, because the side switch wipers 213 and 214 are not allowed to pass to third position. The

shifting of the holding ground of the private magnet 206 to ground G by the relay F e from completing the connection to the called line should the guarding potentialbe removed after the calling subscriber has begun'to receive the busy signal and before the switches have been released. The'switohes or controlled'by a are released from this position by the hanging up of the receiver at the calling substation in the same manner as when a successful connection is completed. Although the side switch is in second position the rotary magnet 209 is not operated in this case by the denergization of the relay 185, because the circuit of said magnet is open at the springs 210 and 211.

From the foregoing it will be seen that,

I provide an automatic trunk-selecting switch having wlpers which travel by a continuous mOtlOn from one trunk terminal-t0 another, as distinguished from-the step-by step motion heretofore employed for this purpose, and in which the said'continuous motion is supplied through an electric motor through the medium of a springs The.

bontinuous motion of the wipers 124 from one trunk terminal to another is regulated the wipers from moving too fast, andthe motive'power is always inreadiness to supgovernor, which prevents,

ply the desired motion, as the spring 109 is normally under tension. All that is necessary is to simply release the governor, and the power'of the said spring instantly starts the motion of the wipers 124, as well as the plungers of the line switches. When the governor is released by the energizing of the relay 116, the wipers of the switch may then move by one continuous motion from one end of the bank of line terminals to the other should the trunks all be busy. This, it will be seen, is different from the old arrangement in which the wipers have a stepby-step motion from one trunk terminal to another throughout the range of their motion, which step-bysstep movement was accomplished by an electromagnetically-operated ratchet mechanism. With my proved arrangement, however, the circuit of the motor 101 is always closed, and the all that is necessary is to simply withdraw the brake or stop from the mechanism by which it is normally held against motion. In other Words, the motive power is being exerted all the time, and to operate the mechanism all that is necessary is to simply release it by the energizing of a single relay.

What I claim as my invention is 1'. In a telephone system, a plurality of trunks having terminals arranged in a row, a'movable element adapted to move back and forth along said row of terminals, means including a spring for actuating said elementin such back and forth movement,

and electrically-operated means for winding up said spring.

2. In a telephone system, a plurality of trunks provided with terminals arranged in a row, a metallic wiper adapted to traverse said row of terminals in contact therewith, means including a spring for operating said wiper .in such back and forth movement, and electrically-operated means for'wmding up said-spring.

3. In a telephone system, .a plurality of trunks provided wit-hterminals arranged in a row, a metallic wiper adapted to travel along said rowof terminals in contact therewith, means including a springfor propelling said wiper in its operative movement, electrically-operated means for winding up said spring, means normally locking the wiper against motion, electrically-operated means for unlocking the wiper, and means for causing the wiper to stop on the 'terminal of the first idle trunk.

. 4. In a-telephone system, a plurality of trunks provided with terminals arranged in arow, mechanism for, selecting idle trunk terminals, meansincluding a s ring for operating sa d mechanism, an e ectric motor for keeping said-motor normally wound up,

means for normally locking said mechanism non numerical trunking against operation, and an electro-magnet for unlocking the mechanism to permit op ,eration thereof bythe said spring.

5. In a telephone system, a plurality of trunks provided with terminals arranged in a row, means for traversing said row of terminals to select idle trunks, an operating mechanism for said means comprising a gear wheel and a governor wheel, a spring connecting said wheels, means for operating one wheel to wind up said spring, means on said wheels for stopping the motion of the one wheel when the spring is wound up, a governor controlling the motion of the governor'wheel, a catch normally engaging said governor to prevent motion of said mechanism, and a magnetfor operating said catch to permit selection of an idle trunk. 6. In a telephone system, a plurality of trunks provided with terminals arranged in a row, mechanism for selecting idle trunk terminals, a motor normally under currentfor supplying power to. operate said mechanism, means for normally locking said mechanism against operation, and means for unlocking the mechanism to permit selection of an idle trunk.

7. In a. telephone system, a plurality of trunksprovided with terminals arranged in a row, mechanism for automatically selecting idle trunk terminals, means normally exerting power to operate said mechanism, means for normally holding the said mechanism stationary, and means for releasing said mechanism to permit selection of an idle trunk.

8. Ina telephone system, a plurality of switches, each switch provided with a bank of trunk terminals, a plunger for each bank of terminals, a shaft for operating said plungers, and an electric motor normally under current for operating sai'd shaft. g

9. In. a telephone system, a plurality of non-numerical trunking switches, each switch provided with a bank of trunk terminals, a plunger for each bank of terminals, a shaft for operating said plungers, an electric motor normally under current for operating said shaft, and a spring interposed between said electric motor and said shaft. 10. In a telephone system, a plurality ofnon-numerical trunking switches, each switch provided with a bank of trunk ter-- minals, a plunger for each bank of terminals, a shaft for operating said plungers, an electric motor' normally under current for operating said shaft, means for holding the shaft stationary, and means for unlocking the shaft to permit rotation thereof by said motor.

11. In a telephone system, a plurality of non-numerical trunking switches, each switch provided with a bank of trunk terminals, a plunger for each bank of terminals, a shaft for operating said plungers, an electric motor normally under current for operating said shaft, a spring interposed between said electric motor and said shaft, means for holding the shaft stationary, and means for unlocking the shaft to permit rotation thereof by said motor and spring.

12. In a telephone system, a plurality of trunk terminals, mechanism for automati cally selecting idle trunk terminals, and means for operating said mechanism com prising a wheel with a ball and socket-joint thereon, said joint beingadjustable toward and away from the axis of said wheel, an arm engaging said ball and socket joint, and an oscillating shaft operated by said arm.

13. In a telephone system, 'a plurality of trunks, mechanism for automatically select ing idle trunks, a governor for controlling said mechanism, means normally locking the governor against mot-ion to prevent operation of said mechanism, and means for unlocking said governor to permit operation of said mechanism.

14:. Ln a telephone system, a plurality of trunks, mechanism for automatically selecting idle trunks, and means for operating said mechanism comprising an oscillatingelement, an arm by which said element is operated, and rota y means for operating said arm, said rotary means provided with a portion whichengages said arm and which is adjustable toward and away from the axis of said rotary means to vary the stroke of said 'arm.I

15. In a telephone system, a plurality of trunk terminals, mechanism for automatically selecting idle trunk terminals, and means for operating said mechanism comprising a wheel, a ball mounted in an opening in said wheel, an arm engaging said ball, and an oscillating shaft operated by said arm.

16. In a telephone system, a plurality of trunk terminals, mechanism for automatically selecting idle trunk terminals, and

means for operatingsaid mechanism com-- prising a wheel, a ball mounted in an opening in said wheel, an arm engaging said ball, an oscillating shaft operated by said arm,

and means for adjusting said ball toward v and away from the axis of said wheel.

17. in a telephone system, a plurality of trunk terminals, mechanism for automatically selecting idle trunk terminals, means for opcrating saidmechanism, said means including a rotary element and an oscillating element, and means by which the rotation of said first element oscillates said second element, said means including an arm connected to said oscillating element and engaging a ball held within said rotary element.

18. In, atele hone system, a-p1uia1ity of -5 including a rotary elementand an oscillat- 4 ing element, means by: which the rotation of sa1d-fii-st element oscillates said second element,"sa 1d-means including an arm connected to said oscillating element and engaging ball in said notary element. I

Signed by me at Chicago, Cook county,

Illinois, this 27 da of April, 1910.

' IICHAEL SETTER. Witnesses: I

v EDWARD D. FALEB, Alum J. RAY.

co m 5mm tent my be obtllncd in: m cent uchfliy addressing the F cum-um: of Patent. 

